U.S. Pat. No. 3,646,177 to Thompson discloses a method for producing powdered metals and alloys that are free from oxidation by a process which involves atomizing molten metal with a fluid jet to form discrete particles of the molten metal. The jet is directed into a reservoir of an inert cryogenic liquid to solidify the particles and prevent oxidation during cooling.
U.S. Pat. No. 4,069,045 to Lundgren describes a process wherein a jet of molten metal is impinged against a rotating flat disc. Relatively thin, brittle, easily shattered, and essentially dentrite free metal flakes are obtained. These flakes are also described in U.S. Pat. No. 4,063,942 to Lundgren.
U.S. Pat. No. 4,221,587 to Ray relates to a method of making powder by impinging a jet of molten alloy at an acute angle against the inner surface of a rotating cylindrical chill body. As set forth in column 5, the impinging molten breaks into a stream of discrete droplets which bounce off the surface and move in the direction of the chill surface. Upon impact with the chill surface, the droplets are solidified at a rapid rate. As set forth in column 6, "the glassy metal powder particles . . . have relatively sharp notched edges which enable the particles to interlock during compaction." As set forth in the first example, the particle size of the powder is such that 90% of the particles have a particle size range between about 25 and 300 microns. In the second example, the particle size of the powder ranges between 100 and 1000 microns.
Herbert Herman and Hareesh Bhat, in an article entitled "Metastable Phases Produced by Plasma Spraying" appearing in the proceedings of a symposium sponsored by the TMS-AIME alloy Phases Committee at the Fall meeting of the Metallurgical Society of AIME, Pittsburgh, Pa., Oct. 5-9, 1980 describes the high velocity deposition of plasma-melting particles on a substrate. On page 118, the article indicates that good physical and thermal contact should exist between the solidifying liquid and substrate. Liquid spreading occurs away from the impact point. As illustrated in the drawings, the particles have a flat surface adjacent the substrate with a central raised core region and a circular rim area.